1. Field of the Invention
The present invention relates to an electrically driven explosion-proof painting robot for use in a painting booth having an environment containing inflammable gases, in particular, the robot has pressurized chambers which may contain ignitable electric motors, cables and other electric equipments.
2. Description of Related Art
U.S. Pat. No. 4,984,745 and 5,421,218 disclose an electrically driven explosion-proof painting robot having pressurized chambers which are in fluid communication with one another and may contain ignitable electric motors and cables, therein. Non-explosion-proof cables housed in a shielding steel air pipe and supplied with pressurized air, supply electric power to the robot motors. U.S. Pat. No. 5,212,432 discloses an electrically driven explosion-proof painting robot having explosion-proof containers containing hollow electric motors. The motor containers are supplied with pressurized air independently via respective input ports and purged via respective output ports through respective pressurized hoses. Further, the '432 patent proposes a robot which houses these hoses inside the robot.
However, in the '745 and '218 patents, the cables extending via an opening between the neighboring pressurized chambers are likely to be affected by abrupt bendings and twistings in a short portion around the opening arising out of relative movement of the neighboring chambers which may damage the cables. Further, it also may take a long time to purge gases or air from all pressurized chambers, and when any one of the pressurized chambers leaks, it may not be possible to detect at once the chamber which has leaked. Further; supply of air pressure to the pressurized chambers drops, it may take too long a time to purge air from the pressurized chambers. In the '432 patent, the hollow electric motors are expensive and the respective pressurized supplying and purging hoses are exposed outside the robot body. Consequently additional installation floor space is required and friction between the exposed hoses and operating robot arms or painting apparatuses is liable to cause damage to the hoses. Further, the robot which houses these hoses inside the robot has a drawback in that it may damage the hoses through friction therebetween.